Method for manufacturing a polarizing film, and method for manufacturing a polarization film

Abstract

The present invention provides a method for manufacturing a polarizing film, the method comprising: a step (I-1) of transporting a polyvinyl alcohol film in the longitudinal direction while performing at least a dyeing step, a crosslinking step, and a stretching step on the polyvinyl alcohol film to manufacture a polarizing film containing water; a step (I-2) of applying a liquid to the obtained polarizing film containing water to manufacture a polarizing film impregnated with components in the liquid; and a step (I-3) of drying the obtained polarizing film impregnated with components in the liquid to manufacture a dried polarizing film, wherein the contact angle of the polarizing film containing water with respect to the liquid is 55° or less. The method for manufacturing a polarizing film of the present invention can simply and sufficiently contain any components in the polarizing film.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a polarizing film and a method for manufacturing a polarization film. Background Art

[0002] Conventionally, as a polarizing film (polarizer) used for various image display devices such as liquid crystal display devices and organic EL display devices, a polyvinyl alcohol-based film that has been subjected to a dyeing treatment (containing dichroic substances such as iodine and dichroic dyes) has been used in consideration of simultaneously achieving high transmittance and high degree of polarization. The polarizing film is manufactured as follows: after performing various treatments such as dyeing, crosslinking, and stretching on the polyvinyl alcohol-based film in a bath (treatment bath), it is dried. In addition, the above-mentioned polarizing film is usually used in the form of a polarization film (polarization plate) in which a protective film such as cellulose triacetate is adhered to one or both sides thereof using an adhesive.

[0003] As a method for manufacturing a polarizing film, for example, Patent Documents 1 to 2 disclose a method for improving the durability characteristics of a polarizing film by adding components such as metal salts containing zinc, copper, aluminum, etc. to a treatment bath so that the polarizing film contains these components. In addition, Patent Documents 3 to 4 disclose a method for manufacturing a polarizing film in which an organotitanium compound or the like is added to a treatment bath.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: International Publication No. 2016 / 117659

[0007] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2006-047978

[0008] Patent Document 3: Japanese Unexamined Patent Application Publication No. 2008-46257

[0009] Patent Document 4: Japanese Unexamined Patent Application Publication No. 6-172554 Summary of the Invention

[0010] Problems to be Solved by the Invention

[0011] However, in the method for manufacturing a polarizing film, when adding the above-mentioned components to a treatment bath, there are problems such as a huge amount of their usage and the need for waste liquid treatment of the treatment liquid.

[0012] In view of the above circumstances, an object of the present invention is to provide a method for manufacturing a polarizing film that can simply and sufficiently contain an arbitrary component in the polarizing film.

[0013] In addition, an object of the present invention is to provide a method for manufacturing a polarization film using the polarizing film obtained by the above-mentioned method for manufacturing a polarizing film.

[0014] Method for solving problems

[0015] That is, the present invention relates to a method for manufacturing a polarizing film, the method comprising: a step (I-1) of transporting a polyvinyl alcohol-based film in the longitudinal direction while subjecting the polyvinyl alcohol-based film to at least a dyeing step, a crosslinking step, and a stretching step, thereby manufacturing a polarizing film containing water; a step (I-2) of subjecting the obtained polarizing film containing water to a step of coating a liquid, thereby manufacturing a polarizing film impregnated with components in the liquid; and a step (I-3) of subjecting the obtained polarizing film impregnated with components in the liquid to a drying step, thereby manufacturing a dried polarizing film, wherein the contact angle of the polarizing film containing water with respect to the liquid is 55° or less.

[0016] In addition, the present invention relates to a method for manufacturing a polarizing film, the method comprising: a step (II-0) of preparing a laminate by forming a polyvinyl alcohol-based resin layer containing a polyvinyl alcohol-based resin on one side of a strip-shaped thermoplastic resin substrate; a step (II-1) of transporting the obtained laminate in the longitudinal direction while subjecting the laminate to at least an auxiliary stretching treatment step in a gas atmosphere, a dyeing treatment step, and a stretching treatment step in an aqueous solution, thereby manufacturing a laminate having a polarizing film containing water; a step (II-2) of subjecting the obtained laminate having a polarizing film containing water to a step of coating a liquid, thereby manufacturing a laminate having a polarizing film impregnated with components in the liquid; and a step (II-3) of subjecting the obtained laminate having a polarizing film impregnated with components in the liquid to a drying treatment step, thereby manufacturing a dried polarizing film, wherein the contact angle of the polarizing film in the laminate having a polarizing film containing water with respect to the liquid is 55° or less.

[0017] In addition, the present invention relates to a method for manufacturing a polarizing film, the method comprising: a step of laminating a transparent protective film via an adhesive layer on at least one surface of the polarizing film obtained by the above method for manufacturing a polarizing film.

[0018] Effects of the invention

[0019] The detailed mechanism of the effects in the method for manufacturing a polarizing film of the present invention is partially unclear, but is presumed as follows. However, the present invention can be interpreted without being limited to this mechanism.

[0020] The manufacturing method of the polarizing film of the present invention includes: a step (I-1) of manufacturing a polarizing film containing water by transporting a polyvinyl alcohol film in the longitudinal direction while performing at least a dyeing step, a crosslinking step, and a stretching step on the polyvinyl alcohol film; a step (I-2) of manufacturing a polarizing film impregnated with the components in the liquid by performing a step of coating the liquid on the obtained polarizing film containing water; and a step (I-3) of manufacturing a dried polarizing film by performing a drying step on the obtained polarizing film impregnated with the components in the liquid, wherein the contact angle of the polarizing film containing water with respect to the liquid is 55° or less. Alternatively, the manufacturing method of the polarizing film of the present invention includes: a step (II-0) of preparing a laminate by forming a polyvinyl alcohol resin layer containing a polyvinyl alcohol resin on one side of a long thermoplastic resin substrate; a step (II-1) of manufacturing a laminate having a polarizing film containing water by transporting the obtained laminate in the longitudinal direction while performing at least an auxiliary stretching treatment step in a gas atmosphere, a dyeing treatment step, and a stretching treatment step in an aqueous solution on the laminate; a step (II-2) of manufacturing a laminate having a polarizing film impregnated with the components in the liquid by performing a step of coating the liquid on the obtained laminate having a polarizing film containing water; and a step (II-3) of manufacturing a dried polarizing film by performing a drying treatment step on the obtained laminate having a polarizing film impregnated with the components in the liquid, wherein the contact angle of the polarizing film in the laminate having a polarizing film containing water with respect to the liquid is 55° or less. In the existing manufacturing method of the polarizing film, after performing at least a dyeing step, a crosslinking step, and a stretching step on the polyvinyl alcohol film, a drying step is then performed. Alternatively, in the existing manufacturing method of the polarizing film, after a step of preparing a laminate by forming a polyvinyl alcohol resin layer containing a polyvinyl alcohol resin on one side of a long thermoplastic resin substrate and performing at least an auxiliary stretching treatment step in a gas atmosphere, a dyeing treatment step, and a stretching treatment step in an aqueous solution on the obtained laminate, a drying treatment step is then performed. On the other hand, in the manufacturing method of the polarizing film of the present invention, a polarizing film containing water or a laminate having a polarizing film containing water is manufactured as described above. Since the contact angle of the polarizing film in the polarizing film containing water or the laminate having a polarizing film containing water with respect to the liquid is 55° or less, any component contained in the liquid can be simply and sufficiently impregnated into the polarizing film containing water. Detailed Embodiments

[0021] <Manufacturing Method of Polarizing Film>

[0022] The method for manufacturing a polarizing film of the present invention includes: a step (I-1) of transporting a polyvinyl alcohol-based film in the longitudinal direction while subjecting the polyvinyl alcohol-based film to at least a dyeing step, a crosslinking step, and a stretching step to manufacture a polarizing film containing water; a step (I-2) of applying a liquid to the obtained polarizing film containing water to manufacture a polarizing film impregnated with the components in the liquid; and a step (I-3) of drying the obtained polarizing film impregnated with the components in the liquid to manufacture a dried polarizing film, wherein the contact angle of the polarizing film containing water with respect to the liquid is 55° or less.

[0023] <Step (I-1) of manufacturing a polarizing film containing water>

[0024] The method for manufacturing a polarizing film of the present invention includes: a step (I-1) of transporting a polyvinyl alcohol-based film in the longitudinal direction while subjecting the polyvinyl alcohol-based film to at least a dyeing step, a crosslinking step, and a stretching step to manufacture a polarizing film containing water.

[0025] The above polyvinyl alcohol (PVA)-based film can be used without particular limitation as a polyvinyl alcohol (PVA)-based film having light transmittance in the visible light region and obtained by dispersing and adsorbing dichroic substances such as iodine and dichroic dyes. In addition, the thickness of the PVA-based film usually used in the form of a film roll is about 1 to 100 μm, more preferably about 1 to 50 μm, and the width is preferably about 100 to 5000 mm.

[0026] Examples of the material of the above polyvinyl alcohol-based film include polyvinyl alcohol or its derivatives. Examples of the derivatives of the above polyvinyl alcohol include: polyvinyl formal, polyvinyl acetal; olefins such as ethylene and propylene; derivatives obtained by modifying with unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid and their alkyl esters, acrylamide, etc. The average degree of polymerization of the above polyvinyl alcohol is preferably about 100 to 10000, more preferably about 1000 to 10000, and further preferably about 1500 to 4500. In addition, the saponification degree of the above polyvinyl alcohol is preferably about 80 to 100 mol%, more preferably about 95 mol% to 99.95 mol%. It should be noted that the above average degree of polymerization and the above saponification degree can be determined based on JIS K6726.

[0027] Additives such as a plasticizer and a surfactant can be included in the above polyvinyl alcohol-based film. Examples of the above plasticizer include: polyhydric alcohols such as glycerin, diglycerin, triglycerin, ethylene glycol, propylene glycol, polyethylene glycol and their condensates, etc. The amount of the above additives is not particularly limited. For example, it is appropriate to be 20% by weight or less in the polyvinyl alcohol-based film.

[0028] <Dyeing step>

[0029] The dyeing process is a treatment process of immersing the polyvinyl alcohol film in a dyeing bath, so that dichroic substances such as iodine or dichroic dyes can be adsorbed on the polyvinyl alcohol film and oriented. The dyeing solution is usually preferably an iodine aqueous solution, and more preferably contains iodine and an iodide as a dissolution aid. It should be noted that as the iodide, potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, titanium iodide, etc. can be listed. Among these, potassium iodide is preferred.

[0030] The concentration of iodine in the dyeing bath is preferably about 0.01 to 1 wt%, more preferably about 0.02 to 0.5 wt%. The concentration of the iodide in the dyeing bath is preferably about 0.01 to 10 wt%, more preferably about 0.05 to 5 wt%.

[0031] The temperature of the dyeing bath is preferably about 10 to 50° C., more preferably about 15 to 45° C. In addition, the immersion time in the dyeing bath cannot be determined without exception because the degree of dyeing of the polyvinyl alcohol film is affected by the temperature of the dyeing bath, but is preferably about 10 to 300 seconds, more preferably about 20 to 240 seconds. The dyeing step may be performed only once or a plurality of times as necessary.

[0032] <Cross-linking process>

[0033] The cross-linking process is a process in which the polyvinyl alcohol film dyed by the dyeing process is immersed in a treatment bath (cross-linking bath) containing a boron compound. The polyvinyl alcohol film can be cross-linked by the boron compound so that iodine molecules or dye molecules are adsorbed on the cross-linked structure. Examples of the boron compound include boric acid, borates, borax, etc. The cross-linking bath is generally an aqueous solution, and can also be a mixed solution of an organic solvent and water that is miscible with water. In addition, the cross-linking bath can contain iodides such as potassium iodide.

[0034] In the cross-linking bath, the concentration of the boron compound is preferably about 1 to 15% by weight, more preferably about 1.5 to 10% by weight, and further preferably about 2 to 5% by weight. In addition, when an iodide such as potassium iodide is used in the cross-linking bath, the concentration of the iodide such as potassium iodide in the cross-linking bath is preferably about 1 to 15% by weight, more preferably about 1.5 to 10% by weight.

[0035] The temperature of the above-mentioned crosslinking bath is preferably about 20 to 70 °C, more preferably about 30 to 60 °C. In addition, regarding the immersion time in the above-mentioned crosslinking bath, the degree of crosslinking of the polyvinyl alcohol-based film is affected by the temperature of the crosslinking bath, so it cannot be determined generally. It is preferably about 5 to 300 seconds, more preferably about 10 to 200 seconds. The above-mentioned crosslinking step can be carried out only once, and can also be carried out multiple times as needed.

[0036] <Stretching step>

[0037] The above-mentioned stretching step is a processing step of stretching the polyvinyl alcohol-based film in at least one direction at a given magnification. Generally, the polyvinyl alcohol-based film is unidirectionally stretched in the conveying direction (length direction). The method of the above-mentioned stretching is not particularly limited, and any method of wet stretching method and dry stretching method can be adopted. The above-mentioned stretching step can be carried out only once, and can also be carried out multiple times as needed. The above-mentioned stretching step can be carried out at any stage in the manufacture of the polarizing film.

[0038] In the above-mentioned wet stretching method, the treatment bath (stretching bath) can usually use solvents such as water, or a mixed solution of an organic solvent miscible with water and water. The above-mentioned stretching bath can contain iodides such as potassium iodide. When iodides such as potassium iodide are used in the above-mentioned stretching bath, in this stretching bath, the concentration of iodides such as potassium iodide is preferably about 1 to 15% by weight, more preferably about 2 to 10% by weight. In addition, in order to increase the degree of crosslinking, the above-mentioned boron compound can be contained in the above-mentioned treatment bath (stretching bath). In this case, in this stretching bath, the concentration of the above-mentioned boron compound is preferably about 1 to 15% by weight, more preferably about 1.5 to 10% by weight.

[0039] The temperature of the above-mentioned stretching bath is preferably about 25 to 80 °C, more preferably about 40 to 75 °C. In addition, regarding the immersion time in the above-mentioned stretching bath, the degree of stretching of the polyvinyl alcohol-based film is affected by the temperature of the stretching bath, so it cannot be determined generally. It is preferably about 10 to 800 seconds, more preferably about 30 to 500 seconds. It should be noted that the stretching treatment in the above-mentioned wet stretching method can be carried out together with any one or more of the above-mentioned dyeing step, the above-mentioned crosslinking step, the swelling step described later, and the cleaning step described later.

[0040] Examples of the above-mentioned dry stretching method include: an inter-roll stretching method, a heated roll stretching method, a compression stretching method, etc. It should be noted that the above-mentioned dry stretching method can be carried out together with the drying step described later.

[0041] The total draw ratio (cumulative draw ratio) applied to the above-mentioned polyvinyl alcohol film can be appropriately set according to the purpose, preferably about 2 to 7 times, more preferably about 3 to 6.8 times, and still more preferably about 3.5 to 6.5 times.

[0042] In the process of manufacturing the above-mentioned polarizing film containing water, in addition to performing the above-mentioned dyeing process, crosslinking process, and stretching process on the above-mentioned polyvinyl alcohol film, a swelling process may also be performed, and a cleaning process may also be performed.

[0043] <Swelling process>

[0044] The above-mentioned swelling process is a treatment process of immersing the polyvinyl alcohol film in a swelling bath, which can remove dirt, anti-sticking agents, etc. on the surface of the polyvinyl alcohol film. In addition, uneven dyeing can be suppressed by swelling the polyvinyl alcohol film. The above-mentioned swelling bath usually uses a medium mainly composed of water such as water, distilled water, and pure water. Surfactants, alcohols, etc. can be appropriately added to the above-mentioned swelling bath according to the usual method.

[0045] The temperature of the above-mentioned swelling bath is preferably about 10 to 60 °C, more preferably about 15 to 45 °C. In addition, regarding the immersion time in the above-mentioned swelling bath, since the swelling degree of the polyvinyl alcohol film is affected by the temperature of the swelling bath, it cannot be determined generally. It is preferably about 5 to 300 seconds, more preferably about 10 to 200 seconds. The above-mentioned swelling process can be performed only once, and can also be performed multiple times as needed.

[0046] <Cleaning process>

[0047] The above-mentioned cleaning process is a treatment process of immersing the polyvinyl alcohol film in a cleaning bath, which can remove foreign substances remaining on the surface of the polyvinyl alcohol film, etc. The above-mentioned cleaning bath usually uses a medium mainly composed of water such as water, distilled water, and pure water. In addition, iodides such as potassium iodide can be contained in the above-mentioned cleaning bath. In this case, in the above-mentioned cleaning bath, the concentration of iodides such as potassium iodide is preferably about 1 to 10% by weight, more preferably about 2 to 4% by weight, and still more preferably about 1.6 to 3.8% by weight.

[0048] The temperature of the above-mentioned cleaning bath is preferably about 5 to 50 °C, more preferably about 10 to 40 °C, and still more preferably about 15 to 30 °C. In addition, regarding the immersion time in the above-mentioned cleaning bath, the cleaning degree of the polyvinyl alcohol film is affected by the temperature of the cleaning bath, so it cannot be determined generally. It is preferably about 1 to 100 seconds, more preferably about 2 to 50 seconds, and still more preferably about 3 to 20 seconds. The above-mentioned swelling process can be performed only once, and can also be performed multiple times as needed.

[0049] In addition, additives such as zinc salts, pH regulators, pH buffers, and other salts may be contained in each treatment bath in the above swelling step, the above dyeing step, the above crosslinking step, the above stretching step, and the above cleaning step. Examples of the above zinc salts include zinc halides such as zinc chloride and zinc iodide; inorganic zinc salts such as zinc sulfate and zinc acetate. Examples of the above pH regulators include strong acids such as hydrochloric acid, sulfuric acid, and nitric acid; strong bases such as sodium hydroxide and potassium hydroxide. Examples of the above pH buffers include carboxylic acids such as acetic acid, oxalic acid, and citric acid and their salts; inorganic weak acids such as phosphoric acid and carbonic acid and their salts. Examples of the above other salts include chlorides such as sodium chloride, potassium chloride, and barium chloride; nitrates such as sodium nitrate and potassium nitrate; sulfates such as sodium sulfate and potassium sulfate; and salts of alkali metals and alkaline earth metals.

[0050] <Process (I-2) for manufacturing a polarizing film impregnated with components in a liquid>

[0051] The method for manufacturing a polarizing film of the present invention includes a step (I-2) of applying a liquid to the obtained polarizing film containing water to manufacture a polarizing film impregnated with components in the liquid. Here, the components in the liquid are usually solutes contained in the solution. In addition, the solute may be any substance that can be dissolved or dispersed in the solvent, and as a single compound, it may be a gaseous substance, a liquid substance, or a solid substance. It should be noted that when the solute is a liquid substance (for example, under the conditions of 25 °C and 1 atmosphere), the liquid substance itself (the liquid substance itself) may be a liquid and the components in the liquid.

[0052] In the above step (I-2), from the viewpoint of facilitating the impregnation of the components contained in the liquid and more easily permeating in the thickness direction of the polarizing film, it is preferable that the water content of the polarizing film is 20% by weight or more, more preferably 22% by weight or more, and further preferably 25% by weight or more. Moreover, from the viewpoint of preventing wrinkles during transportation, it is preferable that the water content of the polarizing film is 70% by weight or less, and more preferably 60% by weight or less.

[0053] As the coating method in the above step of applying the liquid, existing coating methods can be applied, and examples include coating methods such as roll coating, spin coating, wire bar coating, dip coating, die coating, curtain coating, spraying, and doctor blade coating (comma coating, etc.). It should be noted that the coating surface of the polarizing film may be one side or both sides.

[0054] From the viewpoint of facilitating the impregnation of the components into the above-described water-containing polarizing film, the components in the above liquid can be water-soluble compounds. It should be noted that the above water-soluble compounds refer to compounds having a solubility of 1 g or more in 100 g of water at 25°C.

[0055] Examples of the components in the above liquid include: zinc salts (zinc halides such as zinc chloride and zinc iodide; inorganic zinc salts such as zinc sulfate and zinc acetate, etc.); organic titanium compounds (alkoxy titanium, titanium chelates, ammonium salts of titanium chelates, acylates of titanium chelates, etc.), organic zirconium (alkoxy zirconium, zirconium chelates, ammonium salts of zirconium chelates, zirconium acylates), alkali metal salts, alkaline earth metal salts, metal halides, etc.

[0056] In addition, examples of the components in the above liquid include compounds having a free radical trapping function (also referred to as free radical scavengers). The above compounds having a free radical trapping function can trap the free radicals generated by heating of the polyvinyl alcohol in the polarizing film and inhibit polyene formation. Therefore, the heat durability of the polarizing film can be improved. From the viewpoint of easily inhibiting polyene formation, compounds having a nitroxyl radical or a nitroxy group are preferably used as the above compounds having a free radical trapping function.

[0057] Examples of the compounds having a nitroxyl radical or a nitroxy group include: compounds having an organic group with the following structure, etc.

[0058] [Chemical formula 1]

[0059]

[0060] (In the general formula (1), R 1 represents an oxygen free radical, and R 2 ~R 5 independently represent a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and n represents 0 or 1). It should be noted that the left side of the dotted line portion in the general formula (1) represents an arbitrary organic group.

[0061] Examples of the compounds having the above organic group include: compounds represented by the following general formulas (2) to (5), etc.

[0062] [Chemical formula 2]

[0063]

[0064] (In the general formula (2), R 1 ~R 5 and n have the same meanings as described above, and R 6 represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an acyl group, or an aryl group.)

[0065] [Chemical formula 3]

[0066]

[0067] (In general formula (3), R 1 ~R 5 and n have the same meanings as described above, and R 7 and R 8 independently represent a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an acyl group, or an aryl group.)

[0068] [Chemical formula 4]

[0069]

[0070] (In general formula (4), R 1 ~R 5 and n have the same meanings as described above, and R 9 ~R 11 independently represent a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an acyl group, an amino group, an alkoxy group, a hydroxyl group, or an aryl group.)

[0071] [Chemical formula 5]

[0072]

[0073] (In general formula (5), R 1 ~R 5 and n have the same meanings as described above, and R 12 represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an amino group, an alkoxy group, a hydroxyl group, or an aryl group.)

[0074] In the above general formulas (1) to (5), from the viewpoint of ease of acquisition, R 2 ~R 5 is preferably an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms. Further, in the above general formula (2), from the viewpoint of ease of acquisition, R 6 is preferably a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, more preferably a hydrogen atom. Further, in the above general formula (3), from the viewpoint of ease of acquisition, it is preferred that R 7 and R 8 are independently a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, more preferably a hydrogen atom. Further, in the above general formula (4), from the viewpoint of ease of acquisition, R 9 ~R 11 is preferably a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. Further, in the above general formula (5), from the viewpoint of ease of acquisition, R 12 is preferably a hydroxyl group, an amino group or an alkoxy group. In the above general formulas (1) to (5), from the viewpoint of ease of acquisition, n is preferably 1.

[0075] In addition, examples of the compound having a nitroxyl radical or a nitro group include the following compounds and the like.

[0076] [Chemical formula 6]

[0077]

[0078] (In the general formula (6), R represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an acyl group, or an aryl group.)

[0079] [Chemical formula 7]

[0080]

[0081] [Chemical formula 8]

[0082]

[0083] In addition, as the component in the above liquid, a compound having a crosslinking function (also referred to as a crosslinking agent) can be cited. The above compound having a crosslinking function reacts with the hydroxyl group of the polyvinyl alcohol of the polarizing film to form a crosslinked structure, thereby improving the durability of the polarizing film against humidification. As the above compound having a crosslinking function, from the viewpoint of improving the humidification durability, in addition to organic compounds having an isocyanate group, an isocyanate-derived functional group, an epoxy group, a carbonyl group, an aziridine ring, a vinyl ether group, a vinyl sulfonyl group, organic titanium compounds (alkoxy titanium, titanium chelate, ammonium salt of titanium chelate, acyl compound of titanium chelate, etc.) and the like can also be cited.

[0084] In addition, as the component in the above liquid, a compound having a function of imparting plasticity (also referred to as a plasticizer) can be cited. The above compound having a function of imparting plasticity can reduce quality defects such as scratches caused by the pressing force by imparting plasticity to the polarizing film. As the above compound having a function of imparting plasticity, for example, ethylene glycol, polyethylene glycol, ethylene glycol derivatives, glycerol, etc. can be cited.

[0085] In addition, as the component in the above liquid, dye compounds (also referred to as dyes) can be cited. The above dye compounds can impart characteristics such as hue adjustment and pattern printing to the polarizing film. As the above dye compounds, for example, azo compounds, anthraquinones, quinophthalone compounds, etc. can be cited.

[0086] The above liquid is affected by the above coating (application) form. Therefore, it cannot be generally determined. From the perspective of enabling the components in the liquid to penetrate with good efficiency, the concentration of the components in the liquid is preferably 0.1% by weight or more, more preferably 1.0% by weight or more. Moreover, from the perspective of preventing quality problems caused by precipitation of the components in the liquid, the concentration of the components in the above liquid is preferably 30% by weight or less, more preferably 20% by weight or less.

[0087] Examples of the above solvent include: water; water-soluble solvents such as methanol, ethanol, ethylene glycol, polyethylene glycol, ethylene glycol derivatives, glycerin, dimethyl sulfoxide, etc.

[0088] The contact angle of the above water-containing polarizing film with respect to the above liquid is 55° or less. From the perspective of facilitating the impregnation of the components contained in the liquid, the contact angle of the above water-containing polarizing film with respect to the above liquid is preferably 50° or less, more preferably 48° or less.

[0089] Regarding the time from after the above step (I-1) until the start of the above step (I-2) (the transportation time of the polarizing film in actual equipment manufacturing), from the perspective of maintaining the moisture contained in the water-containing polarizing film or from the perspective of productivity, at a temperature of about 15°C to 35°C, preferably at a temperature of about 20°C to 30°C, it is preferably 300 seconds or less, more preferably 180 seconds or less, further preferably 60 seconds or less, and even more preferably 10 seconds or less.

[0090] In addition, if necessary, in the above step (I-2), after the step of coating the liquid on the above water-containing polarizing film, a step of impregnating a part of the liquid and removing the remaining liquid can be implemented. Examples of the liquid removal method include wiping removal methods using cotton waste, sponge rolls, etc., suction removal methods, removal methods using air blowing, scraping removal methods using rods, gravure rolls, etc.

[0091] <Step (I-3) of manufacturing the dried polarizing film>

[0092] The manufacturing method of the polarizing film of the present invention includes: a step (I-3) of performing a drying step on the above obtained polarizing film impregnated with the components in the liquid to manufacture a dried polarizing film.

[0093] The above drying step is a step of drying the polarizing film impregnated with the components in the liquid obtained above to obtain a polarizing film, and a polarizing film with a desired moisture content can be obtained through drying. The above drying is performed by any appropriate method, and examples include: natural drying, air drying, heat drying.

[0094] The drying temperature is preferably about 20 to 150° C., more preferably about 25 to 100° C. In addition, the drying time cannot be determined uniformly because the degree of drying of the polarizing film is affected by the drying temperature, but is preferably about 10 to 600 seconds, more preferably about 30 to 300 seconds. The drying step may be performed only once or multiple times as needed.

[0095] From the viewpoint of preventing the occurrence of poor quality such as scratches due to the disappearance of plasticity, the moisture content of the polarizing film after drying is preferably 10% by weight or more, more preferably 12% by weight or more, and from the viewpoint of improving optical properties such as polarization degree, the moisture content is preferably 20% by weight or less, more preferably 16% by weight or less. It should be noted that in the case of a polarizing film after drying with a thickness of about 8 μm or less described later, from the viewpoint of preventing the occurrence of poor quality such as scratches due to the disappearance of plasticity, the moisture content of the polarizing film after drying is preferably 2% by weight or more, more preferably 3% by weight or more, and from the viewpoint of improving optical properties such as polarization degree, the moisture content is preferably 20% by weight or less, more preferably 10% by weight or less.

[0096] The thickness of the polarizing film after drying is preferably about 1 to 30 μm, more preferably about 5 to 25 μm, and further preferably 5 to 20 μm. In particular, in order to obtain a polarizing film having a thickness of about 8 μm or less after drying, the following method for producing a thin polarizing film can be applied, in which a laminate comprising a thermoplastic resin substrate and a polyvinyl alcohol resin layer formed thereon is used as the polyvinyl alcohol film.

[0097] <Method for producing polarizing film (thin polarizing film)>

[0098] The method for manufacturing a polarizing film (thin polarizing film) includes: a step (II-0) of preparing a laminate by forming a polyvinyl alcohol resin layer containing a polyvinyl alcohol resin on one side of a long thermoplastic resin substrate; a step (II-1) of manufacturing a laminate having a polarizing film containing water while conveying the obtained laminate in the length direction, performing at least an auxiliary stretching treatment step in a gas atmosphere, a dyeing treatment step and a stretching treatment step in an aqueous solution on the above-mentioned laminate; a step (II-2) of applying a liquid to the obtained laminate having a polarizing film containing water, and a step (II-3) of manufacturing a polarizing film after drying the obtained laminate having a polarizing film containing water, wherein the contact angle of the polarizing film in the above-mentioned laminate having a polarizing film containing water to the above-mentioned liquid is less than 55°.

[0099] <Step of Preparing Laminated Body (II-0)>

[0100] The manufacturing method of the polarizing film (thin polarizing film) of the present invention includes: a step (II-0) of preparing a laminate by forming a polyvinyl alcohol resin layer (PVA resin layer) containing a polyvinyl alcohol resin (PVA resin) on one side of a strip-shaped thermoplastic resin substrate.

[0101] As a method for producing the above laminate, any appropriate method can be adopted. For example, a method of coating a coating solution containing the above PVA resin on the surface of the above thermoplastic resin substrate and drying it can be cited. The thickness of the above thermoplastic resin substrate is preferably about 20 to 300 μm, more preferably about 50 to 200 μm. The thickness of the above PVA resin layer is preferably about 3 to 40 μm, more preferably about 3 to 20 μm.

[0102] The above thermoplastic resin substrate absorbs water and significantly reduces the tensile stress. From the viewpoint of being able to stretch at a high magnification, the water absorption rate is preferably about 0.2% or more, more preferably about 0.3% or more. On the other hand, for the above thermoplastic resin substrate, from the viewpoint of preventing significant deterioration of the dimensional stability of the thermoplastic resin substrate and causing defects such as deterioration of the appearance of the obtained polarizing film, the water absorption rate is preferably about 3% or less, more preferably about 1% or less. It should be noted that the above water absorption rate can be adjusted, for example, by introducing a modified group into the constituent material of the above thermoplastic resin substrate. The above water absorption rate is a value obtained based on JIS K 7209.

[0103] For the above thermoplastic resin substrate, from the viewpoint of being able to suppress the crystallization of the PVA resin layer and sufficiently ensuring the stretchability of the laminate, its glass transition temperature (Tg) is preferably about 120 °C or lower. In addition, considering the plasticization of the thermoplastic resin substrate using water and the good stretching in an aqueous solution, the glass transition temperature (Tg) is preferably about 100 °C or lower, more preferably about 90 °C or lower. On the other hand, from the viewpoint of preventing deformation of the thermoplastic resin substrate and other defects when coating / drying the coating solution to produce a good laminate, the glass transition temperature of the thermoplastic resin substrate is preferably about 60 °C or higher. It should be noted that the above glass transition temperature can be adjusted, for example, by introducing a modified group into the constituent material of the above thermoplastic resin substrate or heating with a crystallization material. The above glass transition temperature (Tg) is a value obtained based on JIS K 7121.

[0104] As a constituent material of the above-mentioned thermoplastic resin substrate, any suitable thermoplastic resin can be used. Examples of the above-mentioned thermoplastic resin include ester resins such as polyethylene terephthalate resins, cycloolefin resins such as norbornene resins, olefin resins such as polypropylene, polyamide resins, polycarbonate resins, copolymer resins thereof, and the like. Among these, norbornene resins and amorphous polyethylene terephthalate resins are preferred. Further, from the viewpoint that the stretchability of the thermoplastic resin substrate is very excellent and crystallization during stretching can be suppressed, an amorphous polyethylene terephthalate resin is preferably used. Examples of the amorphous polyethylene terephthalate resin include copolymers containing isophthalic acid and / or cyclohexanedicarboxylic acid as dicarboxylic acids, and copolymers containing cyclohexanedimethanol and diethylene glycol as diols.

[0105] Before forming the PVA-based resin layer, the above-mentioned thermoplastic resin substrate can be subjected to a surface treatment (such as corona treatment, etc.), or an adhesion-promoting layer can be formed on the thermoplastic resin substrate. By performing such a treatment, the adhesion between the thermoplastic resin substrate and the PVA-based resin layer can be improved. In addition, the above-mentioned thermoplastic resin substrate can be stretched before forming the PVA-based resin layer.

[0106] The above-mentioned coating liquid is a solution obtained by dissolving a PVA-based resin in a solvent. Examples of the above-mentioned solvent include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, polyhydric alcohols such as trimethylolpropane, amines such as ethylenediamine and diethylenetriamine, and water is preferred. These solvents can be used alone or in combination of two or more. From the viewpoint of forming a uniform coating film that adheres to the thermoplastic resin substrate, the concentration of the PVA-based resin in the above-mentioned coating liquid is preferably about 3 to 20 parts by weight with respect to 100 parts by weight of the solvent.

[0107] From the viewpoint of improving the orientation of polyvinyl alcohol molecules based on stretching, it is preferable to add a halide to the above-mentioned coating liquid. As the above-mentioned halide, any suitable halide can be used, and examples include iodides and sodium chloride. Examples of the above-mentioned iodide include potassium iodide, sodium iodide, lithium iodide, etc., and potassium iodide is preferred. The concentration of the above-mentioned halide in the above-mentioned coating liquid is preferably about 5 to 20 parts by weight, more preferably about 10 to 15 parts by weight, with respect to 100 parts by weight of the PVA-based resin.

[0108] In addition, an additive can be added to the above-mentioned coating liquid. Examples of the above-mentioned additive include plasticizers such as ethylene glycol and glycerin; surfactants such as nonionic surfactants.

[0109] As the coating method of the above coating liquid, any suitable method can be adopted, and examples thereof include: roll coating method, spin coating method, wire bar coating method, dip coating method, die coating method, curtain coating method, spraying method, doctor blade coating method (comma coating method, etc.). In addition, the drying temperature of the above coating liquid is preferably about 50°C or higher.

[0110] <Process (II-1) for producing a laminate having a polarizing film containing water>

[0111] The method for producing a polarizing film (thin polarizing film) of the present invention includes: while transporting the above-obtained laminate in the length direction, at least subjecting the laminate to an auxiliary stretching treatment process, a dyeing treatment process, and a stretching treatment process in an aqueous solution in a gas atmosphere, thereby producing a laminate having a polarizing film containing water (Process (II-1)).

[0112] In the above auxiliary stretching treatment process in a gas atmosphere, in order to perform stretching while suppressing the crystallization of the thermoplastic resin substrate, the laminate can be stretched at a high magnification. The stretching method in the above auxiliary stretching treatment process in a gas atmosphere can be fixed-end stretching (for example, a method of stretching using a tenter), or free-end stretching (for example, a method of performing unidirectional stretching by passing the laminate between rollers having different circumferential speeds). From the viewpoint of obtaining high optical properties, free-end stretching is preferred.

[0113] The stretching ratio in the above auxiliary stretching process in a gas atmosphere is preferably about 2 to 3.5 times. The above auxiliary stretching process in a gas atmosphere can be carried out in one stage or in multiple stages. In the case of carrying out in multiple stages, the stretching ratio is the product of the stretching ratios of each stage.

[0114] The stretching temperature in the above auxiliary stretching process in a gas atmosphere can be set to any appropriate value according to the forming material of the thermoplastic resin substrate, the stretching method, etc. For example, it is preferably above the glass transition temperature (Tg) of the thermoplastic resin substrate, more preferably above the glass transition temperature (Tg) + 10°C, and further preferably above the glass transition temperature (Tg) + 15°C. On the other hand, from the viewpoint of suppressing the rapid progress of crystallization of the PVA-based resin and suppressing defects caused by crystallization (for example, hindering the orientation of the PVA-based resin layer based on stretching), the upper limit of the stretching temperature is preferably about 170°C.

[0115] As needed, the insolubilization treatment step can be carried out after the auxiliary stretching treatment step in the above gas atmosphere, before the dyeing treatment step and the stretching treatment step in an aqueous solution. The insolubilization treatment step is typically carried out by immersing the PVA-based resin layer in an aqueous boric acid solution. By carrying out the insolubilization treatment step, water resistance can be imparted to the PVA-based resin layer, and the orientation of PVA when immersed in water can be prevented from decreasing. With respect to 100 parts by weight of water, the concentration of the aqueous boric acid solution is preferably about 1 to 5 parts by weight. The liquid temperature of the insolubilization treatment bath is preferably about 20 to 50 °C.

[0116] The above dyeing treatment step is carried out by dyeing the PVA-based resin layer with iodine. As such an adsorption method, for example, a method of immersing the PVA-based resin layer (laminate) in a dyeing solution containing iodine; a method of coating the dyeing solution on the PVA-based resin layer; a method of spraying the dyeing solution onto the PVA-based resin layer, etc. are exemplified, and a method of immersing the PVA-based resin layer (laminate) in a dyeing solution containing iodine is preferred.

[0117] With respect to 100 parts by weight of water, the compounding amount of iodine in the above dyeing bath is preferably about 0.05 to 0.5 parts by weight. In order to increase the solubility of iodine in water, the above iodide is preferably compounded in the iodine aqueous solution. With respect to 100 parts by weight of water, the compounding amount of the iodide is preferably about 0.1 to 10 parts by weight, more preferably about 0.3 to 5 parts by weight. In order to suppress the dissolution of the PVA-based resin, the liquid temperature of the dyeing bath is preferably about 20 to 50 °C. In addition, from the viewpoint of ensuring the transmittance of the PVA-based resin layer, the immersion time is preferably about 5 seconds to 5 minutes, more preferably about 30 seconds to 90 seconds. From the viewpoint of obtaining a polarizing film having good optical properties, the content ratio of iodine and iodide in the iodine aqueous solution is preferably about 1:5 to 1:20, more preferably about 1:5 to 1:10.

[0118] As needed, the crosslinking treatment step can be carried out after the above dyeing treatment step and before the stretching treatment step in an aqueous solution. The crosslinking treatment step is typically carried out by immersing the PVA-based resin layer in an aqueous boric acid solution. By carrying out the crosslinking treatment step, water resistance can be imparted to the PVA-based resin layer, and during the subsequent stretching in an aqueous solution, the orientation of PVA when immersed in high-temperature water can be prevented from decreasing. With respect to 100 parts by weight of water, the boric acid concentration of the aqueous boric acid solution is preferably about 1 to 5 parts by weight. In addition, when carrying out the crosslinking treatment step, it is preferable to further compound the above iodide in the crosslinking bath. By compounding the above iodide, the elution of iodine adsorbed on the PVA-based resin layer can be suppressed. With respect to 100 parts by weight of water, the compounding amount of the iodide is preferably about 1 to 5 parts by weight. The liquid temperature of the crosslinking bath (aqueous boric acid solution) is preferably about 20 to 50 °C.

[0119] The stretching process in the above aqueous solution is carried out by immersing the laminate in a stretching bath. According to the stretching process in the aqueous solution, stretching can be carried out at a temperature lower than the glass transition temperature (representatively about 80 °C) of the above thermoplastic resin substrate and the PVA-based resin layer, and stretching can be carried out at a high magnification while suppressing the crystallization of the PVA-based resin layer. The stretching method of the stretching process in the above aqueous solution can be fixed-end stretching (for example, the method of stretching using a tenter), or free-end stretching (for example, the method of unidirectionally stretching the laminate by passing it between rolls with different circumferential speeds). From the viewpoint of obtaining high optical properties, free-end stretching is preferred.

[0120] The stretching process in the above aqueous solution is preferably carried out by immersing the laminate in a boric acid aqueous solution (stretching in a boric acid aqueous solution). By using a boric acid aqueous solution as the stretching bath, the PVA-based resin layer can be imparted with rigidity that can withstand the tension applied during stretching and water resistance that is insoluble in water. The boric acid concentration of the boric acid aqueous solution is preferably 1 to 10 parts by weight, more preferably 2.5 to 6 parts by weight, relative to 100 parts by weight of water. In addition, iodide can be added to the above stretching bath (boric acid aqueous solution). The liquid temperature of the stretching bath is preferably about 40 to 85 °C, more preferably about 60 °C to 75 °C. The immersion time of the laminate in the stretching bath is preferably about 15 seconds to 5 minutes.

[0121] The stretching ratio in the stretching process in the above aqueous solution is preferably about 1.5 times or more, more preferably about 3 times or more.

[0122] It should be noted that the total stretching ratio of the laminate is preferably about 5 times or more, more preferably about 5.5 times or more, relative to the original length of the laminate.

[0123] It is preferred to carry out a cleaning process after the stretching process in the above aqueous solution. The cleaning process is typically carried out by immersing the PVA-based resin layer in an aqueous potassium iodide solution.

[0124] In addition, additives such as zinc salts, pH regulators, pH buffers, and other salts can be contained in each treatment bath of the above dyeing treatment step, the above stretching treatment step in an aqueous solution, the above insolubilization treatment step, the above crosslinking treatment step, and the above cleaning treatment step. Examples of the above zinc salts include zinc halides such as zinc chloride and zinc iodide; inorganic zinc salts such as zinc sulfate and zinc acetate. Examples of the above pH regulators include strong acids such as hydrochloric acid, sulfuric acid, and nitric acid; strong bases such as sodium hydroxide and potassium hydroxide. Examples of the above pH buffers include carboxylic acids such as acetic acid, oxalic acid, and citric acid and their salts; inorganic weak acids such as phosphoric acid and carbonic acid and their salts. Examples of the above other salts include chlorides such as sodium chloride, potassium chloride, and barium chloride; nitrates such as sodium nitrate and potassium nitrate; sulfates such as sodium sulfate and potassium sulfate; and salts of alkali metals and alkaline earth metals.

[0125] <Process (II-2) of manufacturing a laminate having a polarizing film impregnated with components in a liquid>

[0126] The manufacturing method of the polarizing film (thin polarizing film) of the present invention includes a process (II-2) of manufacturing a laminate having a polarizing film impregnated with components in a liquid by subjecting the laminate having a polarizing film containing water obtained above to a process of coating a liquid. For this process (II-2), all of the above process (I-2) of manufacturing a polarizing film impregnated with components in a liquid can be applied, wherein the above liquid is coated on one side of the polarizing film.

[0127] In the above process (II-2), from the viewpoint of facilitating the impregnation of the components contained in the liquid and more easily permeating in the thickness direction of the polarizing film, a state where the moisture content of the polarizing film is 20% by weight or more is preferred, a state where the moisture content of the polarizing film is 22% by weight or more is more preferred, and a state where the moisture content of the polarizing film is 25% by weight or more is further preferred. Moreover, from the viewpoint of preventing wrinkles during transportation, a state where the moisture content of the polarizing film is 70% by weight or less is preferred, and a state where the moisture content of the polarizing film is 60% by weight or less is more preferred.

[0128] The contact angle of the polarizing film in the above laminate having a polarizing film containing water with respect to the above liquid is 55° or less. From the viewpoint of facilitating the impregnation of the components contained in the liquid, the contact angle of the polarizing film in the above laminate having a polarizing film containing water with respect to the above liquid is preferably 50° or less, and more preferably 48° or less.

[0129] For the time from after the above-mentioned step (II-1) until the start of the above-mentioned step (II-2) (the transport time of the laminate with the polarizing film in actual equipment manufacturing), from the viewpoint of retaining the moisture contained in the polarizing film containing water, or from the viewpoint of productivity, at a temperature of about 15°C to 35°C, preferably about 20°C to 30°C, it is preferably 300 seconds or less, more preferably 180 seconds or less, further preferably 60 seconds or less, and even more preferably 10 seconds or less.

[0130] <Process (II-3) for manufacturing the dried polarizing film>

[0131] The method for manufacturing the polarizing film (thin polarizing film) of the present invention includes a step (II-3) of subjecting the above-obtained laminate with a polarizing film impregnated with components in a liquid to a drying treatment step to manufacture a dried polarizing film.

[0132] The above drying treatment step is carried out by any suitable method, and examples include natural drying, air drying, and heat drying. In addition, the above drying treatment step can be carried out by zone heating in which the entire area is heated, or can be carried out by heating the transport rollers (using so-called heating rollers). By drying using heating rollers, the heating curl of the laminate can be efficiently suppressed, thereby manufacturing a polarizing film with excellent appearance. Moreover, since the laminate can be dried while being kept in a flat state, not only curling but also the generation of wrinkles can be suppressed. In addition, from the viewpoint that the optical properties of the obtained polarizing film can be improved by allowing it to shrink in the width direction during the drying treatment step, the shrinkage rate in the width direction of the laminate in the drying treatment step is preferably about 1 to 10%, more preferably about 2 to 8%.

[0133] The drying conditions can be controlled by adjusting the heating temperature of the transport rollers (the temperature of the heating rollers), the number of heating rollers, and the contact time with the heating rollers. The temperature of the heating rollers is preferably about 60 to 120°C, more preferably about 65 to 100°C, and further preferably 70 to 80°C. From the viewpoint that the crystallinity of the thermoplastic resin can be increased well and curling can be suppressed well, usually 2 to 40 heating rollers are provided, preferably 4 to 30 heating rollers are provided. The contact time (total contact time) of the laminate with the heating rollers is preferably about 1 to 300 seconds, more preferably 1 to 20 seconds, and further preferably 1 to 10 seconds.

[0134] The heating roller can be disposed in a heating furnace or in a normal production line (at room temperature environment), and is preferably disposed in a heating furnace equipped with a blowing mechanism. By combining drying using the heating roller and hot air drying, a sharp temperature change between the heating rollers can be suppressed, and thus shrinkage in the width direction can be easily controlled. The temperature of the hot air drying is preferably about 30 to 100 °C. In addition, the hot air drying time is preferably about 1 to 300 seconds.

[0135] <Manufacturing method of polarizing film>

[0136] The manufacturing method of the polarizing film of the present invention includes a step of laminating a transparent protective film via an adhesive layer on at least one surface of the polarizing film obtained by the above-described manufacturing method of the polarizing film.

[0137] The above-mentioned transparent protective film is not particularly limited, and various transparent protective films used in polarizing films can be used. As the material constituting the above-mentioned transparent protective film, for example, thermoplastic resins excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy, etc. can be used. As the above-mentioned thermoplastic resin, for example, cellulose ester resins such as cellulose triacetate, polyester resins such as polyethylene terephthalate and polyethylene naphthalate, polyethersulfone resins, polysulfone resins, polycarbonate resins, polyamide resins such as nylon and aromatic polyamide, polyimide resins, polyolefin resins such as polyethylene, polypropylene, and ethylene-propylene copolymer, (meth)acrylic resins, cyclic or cyclic polyolefin resins having a norbornene structure (norbornene resins), polyarylate resins, polystyrene resins, polyvinyl alcohol resins, and mixtures thereof can be cited. In addition, the above-mentioned transparent protective film can use a cured layer formed of thermosetting resins such as (meth)acrylic, urethane, acrylic urethane, epoxy, and silicone, or ultraviolet curable resins. Among these, cellulose ester resins, polycarbonate resins, (meth)acrylic resins, cyclic polyolefin resins, and polyester resins are preferred.

[0138] The thickness of the above-mentioned transparent protective film can be appropriately determined. Generally, from the viewpoints of strength, processability such as operability, and thin layer property, etc., it is preferably about 1 to 500 μm, more preferably about 1 to 300 μm, and further preferably about 5 to 100 μm.

[0139] When laminating the above-mentioned transparent protective film on both surfaces of the above-mentioned polarizing film, the transparent protective films on both surfaces can be the same or different.

[0140] The above-mentioned transparent protective film can use a retardation plate having a front retardation of 40 nm or more and / or a thickness-direction retardation of 80 nm or more. Generally, the front retardation is controlled within a range of 40 to 200 nm, and the thickness-direction retardation is generally controlled within a range of 80 to 300 nm. When using a retardation plate as the above-mentioned transparent protective film, the retardation plate also functions as a transparent protective film, so that thinning can be achieved.

[0141] Examples of the above-mentioned retardation plate include, for example, a birefringent film obtained by unidirectionally or bidirectionally stretching a polymer raw material, an alignment film of a liquid crystal polymer, a retardation plate formed by supporting an alignment layer of a liquid crystal polymer with a film, etc. The thickness of the retardation plate is not particularly limited, and is usually about 20 to 150 μm. It should be noted that the above-mentioned retardation plate can be used by laminating it on a transparent protective film having no retardation.

[0142] Any suitable additives such as an ultraviolet absorber, an antioxidant, a lubricant, a plasticizer, a release agent, an anti-coloring agent, a flame retardant, an antistatic agent, a pigment, a coloring agent, etc. can be included in the above-mentioned transparent protective film.

[0143] Functional layers such as a hard coat layer, an antireflection layer, an anti-adhesion layer, a diffusion layer, an antiglare layer, etc. can be provided on the side of the above-mentioned transparent protective film that is not adhered to the polarizing film. It should be noted that the above-mentioned functional layers such as the hard coat layer, the antireflection layer, the anti-adhesion layer, the diffusion layer, the antiglare layer, etc. can be provided not only as the protective film itself but also as a layer different from the protective film separately.

[0144] The above-mentioned polarizing film and the above-mentioned transparent protective film, or the above-mentioned polarizing film and the above-mentioned functional layer are usually laminated together with an adhesive layer or a bonding agent layer interposed therebetween.

[0145] As the adhesive for forming the above-mentioned adhesive layer, various adhesives used in polarizing films can be applied, and examples include: rubber-based adhesives, acrylic adhesives, silicone adhesives, urethane adhesives, vinyl alkyl ether adhesives, polyvinyl alcohol adhesives, polyvinylpyrrolidone adhesives, polyacrylamide adhesives, cellulose adhesives, etc. Among these, acrylic adhesives are preferred.

[0146] As a method for forming the adhesive layer, for example, the above-mentioned adhesive is coated on a separator or the like after being subjected to a peeling treatment and dried, and after forming the adhesive layer, it is transferred to a polarizing film or the like; or the above-mentioned adhesive is coated on a polarizing film or the like and dried to form an adhesive layer. The thickness of the above-mentioned adhesive layer is not particularly limited, for example, it is about 1 to 100 μm, preferably about 2 to 50 μm.

[0147] As the adhesive for forming the above adhesive layer, various adhesives used in polarizing films can be applied, and examples include: isocyanate adhesives, polyvinyl alcohol adhesives, gelatin adhesives, vinyl latexes, aqueous polyesters, etc. These adhesives are usually used in the form of adhesives formed from aqueous solutions and contain 0.5 to 60% by weight of solid components.

[0148] As the above adhesive, in addition to the above, examples of energy ray curable adhesives such as ultraviolet curable adhesives and electron beam curable adhesives can be cited. As the above energy ray curable adhesives, examples include (meth)acrylate adhesives. As the curable components in the above (meth)acrylate adhesives, examples include: compounds having a (meth)acryloyl group, compounds having a vinyl group. In addition, as a cationic polymerization curable adhesive, a compound having an epoxy group or an oxetanyl group can also be used. The compound having an epoxy group is not particularly limited as long as it has at least two epoxy groups in the molecule, and various commonly known curable epoxy compounds can be used.

[0149] The coating of the above adhesive can be carried out on either the side of the above transparent protective film (or the side of the above functional layer) or the side of the above polarizing film, or on both sides. After lamination, a drying process is carried out to form an adhesive layer made of a coated and dried layer. After the above drying process, ultraviolet rays or electron beams can be irradiated as needed. The thickness of the above adhesive layer is not particularly limited. In the case of using an aqueous adhesive or the like, it is preferably about 30 to 5000 nm, more preferably about 100 to 1000 nm. In the case of using an ultraviolet curable adhesive, an electron beam curable adhesive, etc., it is preferably about 0.1 to 100 μm, more preferably about 0.5 to 10 μm.

[0150] The above transparent protective film and the above polarizing film, or the above polarizing film and the above functional layer can be laminated with each other with an intervening layer such as a surface modification layer, an easy-bonding layer, a barrier layer, a refractive index adjustment layer, etc.

[0151] As the surface modification treatment for forming the above surface modification layer, examples include: corona treatment, plasma treatment, primer treatment, saponification treatment, etc.

[0152] As the easy-bonding agent for forming the above easy-bonding layer, examples include: forming materials containing various resins having a polyester skeleton, a polyether skeleton, a polycarbonate skeleton, a polyurethane skeleton, a silicone type, a polyamide skeleton, a polyimide skeleton, a polyvinyl alcohol skeleton, etc. The above easy-bonding layer can usually be provided on the protective film in advance, and the easy-bonding layer side of the protective film is laminated with the polarizing film with the above adhesive layer or the above adhesive layer intervening.

[0153] The above-mentioned barrier layer is a layer having a function of preventing the migration (invasion) of impurities such as oligomers and ions eluted from a transparent protective film or the like into the polarizing film. The above-mentioned barrier layer may be any layer that has transparency and can prevent impurities eluted from a transparent protective film or the like. Examples of materials for forming the barrier layer include, for example, urethane prepolymer-based forming materials, cyanoacrylate-based forming materials, epoxy-based forming materials, and the like.

[0154] The above-mentioned refractive index adjustment layer is a layer provided to suppress the reduction in transmittance due to reflection between layers with different refractive indices such as the above-mentioned transparent protective film and the polarizing film. Examples of refractive index adjustment materials for forming the above-mentioned refractive index adjustment layer include, for example, forming materials containing various resins and additives having silica-based, acrylic-based, acrylic-styrene-based, melamine-based, and the like.

[0155] The degree of polarization of the above-mentioned polarizing film is preferably 99.98% or more, and more preferably 99.99% or more.

[0156] Examples

[0157] Hereinafter, examples are given to explain the present invention in more detail, but the present invention is not limited to these examples.

[0158] <Example 1>

[0159] <Manufacture of Polarizing Film>

[0160] <Manufacture (Preparation) of Laminate (II-0)>

[0161] As the thermoplastic resin substrate, an amorphous isophthalic acid copolyethylene terephthalate film (thickness: 100 μm) in a long strip shape with a water absorption rate of 0.75% and a Tg of about 75°C was used. Corona treatment was performed on one side of the resin substrate. 13 parts by weight of potassium iodide was added to 100 parts by weight of a PVA-based resin obtained by mixing polyvinyl alcohol (degree of polymerization 4200, saponification degree 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOHSEFIMER Z410") in a ratio of 9:1 to prepare a PVA aqueous solution (coating solution). The above-mentioned PVA aqueous solution was coated on the corona-treated surface of the resin substrate and dried at 60°C to form a PVA-based resin layer with a thickness of 13 μm, and a laminate was manufactured (prepared).

[0162] <Process for Manufacturing a Laminate Having a Polarizing Film Containing Water (II-1)>

[0163] The obtained laminate was subjected to free-end unidirectional stretching (auxiliary stretching treatment process in a gas atmosphere) to 2.4 times in the longitudinal direction (length direction) between rolls with different circumferential speeds in an oven at 130°C. Subsequently, the laminate was immersed in an insolubilization bath at a liquid temperature of 40°C (an aqueous boric acid solution obtained by adding 4 parts by weight of boric acid to 100 parts by weight of water) for 30 seconds (insolubilization treatment process). Then, in a dyeing bath at a liquid temperature of 30°C (an aqueous iodine solution obtained by mixing iodine and potassium iodide in a weight ratio of 1:7 with respect to 100 parts by weight of water), the concentration was adjusted so that the monomer transmittance (Ts) of the finally obtained polarizing film became the same level, and it was immersed for 60 seconds (dyeing treatment process). Then, it was immersed in a crosslinking bath at a liquid temperature of 40°C (an aqueous boric acid solution obtained by adding 3 parts by weight of potassium iodide and 5 parts by weight of boric acid to 100 parts by weight of water) for 30 seconds (crosslinking treatment process). Then, the laminate was immersed in an aqueous boric acid solution at a liquid temperature of 70°C (boric acid concentration 4.0% by weight), and unidirectional stretching was performed between rolls with different circumferential speeds in the longitudinal direction (length direction) so that the total stretching ratio reached 5.5 times (stretching treatment process in an aqueous solution). Then, the laminate was immersed in a cleaning bath at a liquid temperature of 20°C (an aqueous solution obtained by adding 4 parts by weight of potassium iodide to 100 parts by weight of water), and a laminate having a polarizing film containing water was manufactured (cleaning treatment process).

[0164] <Manufacture of a laminate having a polarizing film impregnated with components in a liquid (II-2)>

[0165] Using a wire bar (manufactured by Daiichi Rika Co., Ltd., No. 3), liquid A (a 10% by weight aqueous solution of the compound represented by Chemical Formula (9)) was coated on the polarizing film surface of the above-obtained laminate having a polarizing film containing water. After standing at 25°C for 3 seconds, the remaining liquid A on the surface was wiped off, and a laminate having a polarizing film impregnated with components in a liquid was manufactured. Here, the moisture content of the polarizing film containing water determined by the following measurement method was 35.5% by weight. In addition, the contact angle of the polarizing film in the laminate having a polarizing film containing water with respect to liquid A determined by the following measurement method was 45.2°.

[0166] [Chemical Formula 9]

[0167]

[0168] [Measurement method for moisture content (wt%) in the polarizing film]

[0169] Approximately 0.2 g of the polarizing film was weighed, dried at 120°C for 2 hours, the weight after drying was measured, and the moisture content (W) in the polarizing film was calculated based on the following formula.

[0170] Moisture content W (wt%) of the polarizing film = { (M0 - M1) / M0} × 100

[0171] M0: Weight of the measured polarizing film (g)

[0172] M1: Weight of the polarizing film after drying at 120 °C for 2 hours (g)

[0173] [Method for measuring the contact angle]

[0174] For the above water-containing polarizing film pasted on a glass slide, the above contact angle was measured by the droplet method in accordance with JIS R 3257. The measurement was carried out 5 times, and the average value was taken as the value of the contact angle.

[0175] Measuring device: Automatic contact angle measuring instrument CA-X type (manufactured by Kyowa Interface Science Co., Ltd.)

[0176] Measuring atmosphere: 23 °C, 50% RH

[0177] Measuring liquid: Liquid A

[0178] Water droplet volume: 1 μL

[0179] Measuring time: 1 second after droplet landing

[0180] <Manufacture of the dried polarizing film (II-3)>

[0181] It was dried in an oven maintained at 95 °C for 10 minutes (drying treatment step). In this way, a polarizing film with a thickness of 5 μm was formed on the resin substrate. The moisture content of the dried polarizing film obtained by the above measurement method was 9.9 wt%. The content (M H ) of the compound represented by Chemical Formula (9) in the polarizing film was 0.41 wt%, and the content (m H ) of the compound represented by Chemical Formula (9) per unit area was 2.5 μg / cm 2 .

[0182] [Method for measuring the content (wt%) of the compound represented by Chemical Formula (9) in the polarizing film]

[0183] Approximately 20 mg of the polarizing film was taken, quantified, heated and dissolved in 1 mL of water, diluted with 4.5 mL of methanol, and the resulting extract was filtered through a membrane filter. The concentration of the compound represented by Chemical Formula (9) in the filtrate was measured using HPLC (ACQUITY UPLC H-class Bio manufactured by Waters Corporation).

[0184] [Method for measuring the content (μg / cm 2 ) of the compound represented by Chemical Formula (9) per unit area of the polarizing film]

[0185] The content (m H ) of the compound represented by Chemical Formula (9) per unit area is calculated based on the following formula.

[0186] m H = 1.2 × T × M H (μg / cm 2 )

[0187] T: Thickness (μm) of the polarizing film

[0188] M H : Content (wt%) of the compound represented by Chemical Formula (9) in the polarizing film

[0189] <Manufacture of the Polarizing Film>

[0190] As the adhesive, an aqueous solution containing polyvinyl alcohol resin having an acetoacetyl group (average degree of polymerization: 1200, saponification degree: 98.5 mol%, acetoacetylation degree: 5 mol%) and hydroxymethyl melamine in a weight ratio of 3:1 was used. Using this adhesive and a roll laminator, a triacetyl cellulose film (moisture permeability: 342 g / (m 2 ·24 h), manufactured by Konica Minolta, trade name "KC4UYW") with a hard coat and a thickness of 40 μm was laminated on both sides of the polarizing film obtained above. Then, it was heated and dried in an oven (temperature: 60°C, time: 4 minutes) to manufacture a polarizing film with transparent protective films laminated on both sides of the polarizing film.

[0191] [Method for Measuring Degree of Polarization]

[0192] The degree of polarization of the polarizing film can be measured using a spectrophotometer (manufactured by JASCO Corporation, product name "V7100"). As a specific method for measuring the degree of polarization, the parallel transmittance (H0) and the orthogonal transmittance (H90) of the polarizing film are measured and calculated according to the formula: Degree of polarization (%) = {(H0 - H90) / (H0 + H90)}1 / 2 × 100. The parallel transmittance (H0) is the transmittance value of a parallel-type laminated polarizing film made by laminating two identical polarizing films with their absorption axes parallel. In addition, the orthogonal transmittance (H90) is the transmittance value of an orthogonal-type laminated polarizing film made by laminating two identical polarizing films with their absorption axes orthogonal. It should be noted that these transmittance values are Y values obtained by performing visibility correction using a 2-degree field of view (C light source) of JlS Z8701-1982.

[0193] [Evaluation of Heat Resistance]

[0194] The obtained polarizing film was cut into a size of 5.0 × 4.5 cm with the absorption axis of the polarizing film parallel to the long side, and a glass plate (simulating an image display unit) was bonded to the protective film surface on the image display unit side of the polarizing film through an acrylic adhesive layer with a thickness of 20 μm. Autoclave treatment was carried out at 50 °C and 0.5 MPa for 15 minutes to fabricate a laminate. The obtained laminate was placed in a hot air oven at a temperature of 95 °C, and the time until coloring was visually observed and judged according to the following criteria.

[0195] ○: No coloring occurred for 750 hours or more.

[0196] △: Coloring occurred at 500 hours or more and less than 750 hours.

[0197] ×: Coloring occurred at less than 500 hours.

[0198] <Example 2>

[0199] <Manufacture of Polarizing Film and Polarization Film>

[0200] After drying the polarizing film after the cleaning treatment process at 60 °C for 1 minute, Liquid A was coated. Except for this, a polarizing film and a polarization film were manufactured by the same operations as in Example 1, and the above-mentioned measurements were carried out. The results are shown in Table 1.

[0201] <Comparative Example 1>

[0202] <Manufacture of Polarizing Film and Polarization Film>

[0203] After drying the polarizing film after the cleaning treatment process at 95 °C for 10 minutes, Liquid A was coated. Except for this, a polarizing film and a polarization film were manufactured by the same operations as in Example 1, and the above-mentioned measurements were carried out. The results are shown in Table 1.

[0204]

Claims

1. A method for manufacturing a polarizing film, the method comprising: Step (I-1): While transporting a polyvinyl alcohol-based film in the longitudinal direction, at least performing a dyeing step, a crosslinking step, and a stretching step on the polyvinyl alcohol-based film to manufacture a polarizing film containing water; Step (I-2): Performing a step of coating a liquid on the obtained polarizing film containing water to manufacture a polarizing film impregnated with components in the liquid; Step (I-3): Performing a drying step on the obtained polarizing film impregnated with components in the liquid to manufacture a dried polarizing film, wherein the moisture content of the dried polarizing film is 10% by weight or more and 20% by weight or less; and A step of coating an adhesive on the coating surface of the liquid of the obtained dried polarizing film and laminating a transparent protective film via the adhesive layer, wherein the contact angle of the polarizing film containing water with respect to the liquid is 50° or less, Alternatively, the method comprises: Step (II-0): Preparing a laminate by forming a polyvinyl alcohol-based resin layer containing a polyvinyl alcohol-based resin on one side of a strip-shaped thermoplastic resin substrate; Step (II-1): While transporting the obtained laminate in the longitudinal direction, at least performing an auxiliary stretching treatment step, a dyeing treatment step, and a stretching treatment step in an aqueous solution on the laminate to manufacture a laminate having a polarizing film containing water; Step (II-2): Performing a step of coating a liquid on the obtained laminate having a polarizing film containing water to manufacture a laminate having a polarizing film impregnated with components in the liquid; Step (II-3): Performing a drying treatment step on the obtained laminate having a polarizing film impregnated with components in the liquid to manufacture a dried polarizing film, wherein the moisture content of the dried polarizing film is 3% by weight or more and 20% by weight or less, and the thickness is 8 μm or less; and, A step of coating an adhesive on the coating surface of the liquid of the obtained dried polarizing film and laminating a transparent protective film via the adhesive layer, wherein the contact angle of the polarizing film in the laminate having a polarizing film containing water with respect to the liquid is 50° or less.

2. The method for manufacturing a polarizing film according to claim 1, wherein the liquid is a solution, and the component in the liquid is a solute.

3. The method for manufacturing a polarizing film according to claim 1 or 2, wherein the component in the liquid is a water-soluble compound.

4. The method for manufacturing a polarizing film according to claim 1 or 2, wherein the component in the liquid is at least one selected from a radical scavenger, a crosslinking agent, a plasticizer, and a dye.

5. The method for manufacturing a polarizing film according to claim 1 or 2, wherein the component in the liquid is a radical scavenger.

Images